Railroad trains use wireless signals to facilitate continuous monitoring and control of the train. These signals include control signals that are sent from the lead locomotive to support locomotives to control braking and acceleration. The support locomotives are generally spaced apart, separated by multiple railroad cars. In addition, signals are sent between an End-of-Train device and a Head-of-Train device to monitor brake pressure and to ensure that the train is intact. However, these wireless signals, which comprise ultra-high frequency (UHF) radio frequencies, are not reliably transmitted when a train enters a shielded environment, such as a tunnel. A previous solution to this problem uses a distributed antenna system comprising radiating coaxial cable and analog bi-directional, in-line amplifiers to extend radio coverage into railroad tunnels.
The inventors of the present disclosure have identified significant issues with the described tunnel communication system. As an example, set-up, maintenance, and troubleshooting of the tunnel communication system requires the presence of on-site technical personnel both at amplifier locations inside the tunnel, and at a system head end outside the tunnel. Furthermore, adjustments of parameters such as amplifier attenuation, switching power, and gain may also demand on site, manual manipulation of the system within the tunnel. Another issue includes difficulty in gaining access to equipment inside an active railroad tunnel which may demand operational down time of a train track.
The issues may be at least partially addressed by a radio communication system having a remotely-controlled distributed antenna system employing software-defined amplifiers. The software-defined amplifiers (SDAs) described herein provides digital controls and expands monitoring capabilities. The SDA also enables amplifier performance parameters, and, therefore, system performance to be remotely controlled. In addition, the SDA is compatible with existing tunnel communication systems and uses networking technology to send and receive data and therefore may be retrofit to already existing systems. Control and monitoring interfaces may be integrated into system head end apparatuses, and may be made as stand-alone remote devices.
The inventors have also identified and implemented aspects that may be beneficial to technicians in the railroad radio communications systems industry. For example, amplifier gain levels may be set in the field without entering a tunnel. Also, an amplifier switching state, e.g., processing of uplink vs. downlink signals, may be controlled remotely or at the system head end. Additional benefits of the radio communication system include eliminating a pilot signal for setting amplifier gain levels, and an ability to store and manipulate system operation data. Furthermore, the ability to remotely-control both attenuation settings and amplifier uplink/downlink settings is achieved by the radio communication system, described herein.
Advantages provided by the software-defined amplifier of the present disclosure further include an ability to monitor a wide variety of system statuses. For example, gain levels, including both uplink and downlink gain may be monitored either from the system head end or from a remote location through a network connection. Similarly, technicians may monitor power levels, such as peak downlink output power and switching signal RF input power. System parameters, such as RF detector voltages, and attenuation levels, including uplink and downlink attenuator settings, may also be monitored. In addition, system characteristics monitored may include SDA switching state and unit temperature.
SDA unit serial numbers can likewise be monitored so that a technician at the head end or at a remote location may identify and isolate data from each individual SDA. Data from each SDA can be stored in a database for evaluation at a later time. Data from individual SDAs can also be compared to other SDAs in the system or to an ideal SDA performance standard at the time of monitoring, or at a later occasion.
The monitoring and control of SDAs described herein has two levels. A first level comprises on-site monitoring and control at a head end location outside the tunnel. The tunnel may be any shielded environment. Once the system hardware is installed, commissioning, monitoring and control of the system can take place at the head end location, without physical presence of an operator inside of the tunnel. A second level comprises network-enabled monitoring and control. If a network connection is available at the site of the head end, monitoring and control may be performed at any remote site coupled to the network connection. The summary above should be understood as providing an introduction in simplified form to a selection of concepts that are further described in the detailed description. The summary is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of the present disclosure.